MG Midget and Sprite Technical Roll Bar Fitting Problem BBS discussion at MG-Cars.net

MG Midget and Sprite Technical - Roll Bar Fitting Problem

The Safety Devices roll bar for my 1967 Austin Healey Sprite Mk IV arrived this week. When I tried to fit the bar I found that the rear bracing bars foul the original seat belt mounting points. The protruding belt mounting stop the bar's mounting bracket from fitting snugly against the body shell. Even if the bar fitted snugly, it would not be possible to fit the seatbelt. Grinding back the belt mounting point would provide the necessary clearance but I am reluctant to remove material and risk weakening the mounting. The front face of the wheel arch, adjacent to the ledge that the main hoop sits on, has been repaired by 'plating' some time in the past. This means that the front hoop sits a few millimetres further forward than originally intended but I don't think this makes much difference as moving the bracing bars back would bring them more directly in line with the seat belt bolt holes. Please see the attached pictures that illustrate the problem. The bar supplied is the correct one according to SD's website's roll cage selector (RBN006S 5SSS)but I am wondering whether there is a slightly different design for cars with these seat belt mounting points. I am intending to do a bit of hill climbing and have a four point harness ready to go in when the bar is in place. I had originally hoped to get a bar with a built in harness bar but didn't want to wait several months for the supplier's next delivery. I would be very grateful for any advice you can offer. Incidentally - the brown in the pics is not rust - it's evostick - and the black is a mixture of cheap carpet and one of the Sprite's many previous colours - the red is original, it has also been black, 'sand' for a while and is currently maroon! Colin

Colin Mee

Colin. We had to do the same to the "junior" car to get it to fit. I have to say that I agree with Daniel in so much as the first race Midget I had was built with an Aley Bar and that one seemed to be a lot better design that the only one you can get currently from SD. It held up well to a multiple barrel roll also. In hindsight I should have kept that cage as there were we no kinks or damage to it. Still it's being put to some good use still at the Marshalls training at Snetterton where the car met its demise. Daniel doesn't need to recommend any particular books as there are quite a few on here who would happily recommend it and I'm one of them. Andrew

Andrew McGee

Here's the passenger side all finished as it is now. You can see where the seat belt mount has been cut out and welded up again. Doing that allows the roll bar to sit nicely square to the arch without being put under load. The seat belt mount is just a cheap 3 point that needs to be fitted as the car has to be road legal.

John Payne

Here is the drivers side when I was in the process of fitting some shocks. Again you can see the removal of the seat belt point. The harness eye is fitted (I think it is 2" long) into the chassis and through into the wheel arch where it threads into a spreader plate with captive nut. You can see the other harness mount (eye not fitted) near the bulkhead. Also, if you look at the bottom left corner of the photo you can see the mounting point I had to weld in to mount the foot of the main hoop of the bar. If this hadn't have been done the top two bolts of the cage were having to pull either the cage or wheel arch in so they met. In fact I dont think they would ever have pulled up hence my making a plinth for the foot to mount on. Looking back it was quite a big job and took a long time to get right. I seem to remember at the time cursing who had designed it! My car had had work and corrosion in that area so maybe was worse to fit than a decent shell. Good luck!!

John Payne

Colin I don't think there's an easy answer to mounting of the 3-point belts for road use; the mount will have to be removed for correct installation of the cage. Personally I'd cut it out, plate it like JP's, then weld the threaded boss back into the top part of the arch. For the 4-point belts you would be best to have a harness bar welded onto the cage before fitting it to the car. This will invalidate the FIA homologation cert but that's only important if you intend to race at an event run to full FIA rules i.e.something posh and expensive abroad. If you don't want a harness bar here's a pic of my installation - on the underside of the rear floor there's a lump of 4mm plate about 25 x 10mm from memory.

David Smith

ROLLBARS for MOTORSPORT Sometimes this is a tricky subject even for an MSA scrutineer and it's more complicated for older cars. First thing is that anyone can make a Roll bar (now called a roll over protection system (ROPS) that is MSA legal by following the drawings in the blue book and tubing specification etc. Most Sprite/Midget owners don't make their own ROPS but buy one off the shelf or buy a secondhand one that someone else bought off the shelf many years previous from a recognised manufacturer like Aley bars or Safetey Devices (SD). What you will find however, is that the Aley or SD bar pretty much follows the drawings and tubing specification in the blue book anyway. HOWEVER, a manufacturer can deviate from the blue book if they get their bar certificated and they nearly all do. With the Sprite/Midget being an old car and no longer in production most of the new ROPS are built to an old certification as it's not worth the trouble of getting a new design certified. There are of course exceptions especially for the Frogeye. For UK motorsport and this will be just be racing I'm writing about, unless the event is an International event run to FIA rules (the MG International is Clubmans/National B) there is NO requirement for the ROPS to have a diagonal though most do. It's also the case therefore that it doesn't matter if the diagonal is removable or not and in fact I don't think I've ever seen a racing Sprite/Midget or road car, other than my own, that has the removable diagonal. In fact I've just checked the certificate for my Aley bar and it was certificated with a removable diagonal as well as having the diagonal left to right or right to left! If I understand the rules correctly the increase in diameter of the tubing is for the home built ROPS. So if a manufacture wants to certify his ROPS with smaller tubing he CAN, though most don't and simply certify broadly along the lines of the latest free build MSA or FIA regulations. So, if SD have an older design of bar that was certificated with 38mm tubing it's still legal but if they never had it certificated it's not. The only roll bars that are NO LONGER LEGAL (where the rules require a legal bar) are those made from aluminium tubing and I assume those certificates were cancelled or never existed in the first place. A point to note is that you can have a certificated Aley bar with small diameter tubing but no diagonal that is MSA race legal but not FIA race legal. However, if the organising club have a more stringent/exceeds MSA ROPS requirement (like a diagonal or full cage) in the supplmentary regs your car has to meet that SR to be race legal on the day. I think the issue about the number of bolt holes in the mounting feet can be found in the archives. Finally, don't forget some padding and homologated padding is generally only a mandatory requirement for a full International event. Final, finally, not sure on the ROPS rules for European events at places such as SPA - they may have historically always been aligned to FIA rules and always want a diagonal.

Daniel Stapleton

RollCentre bar received and fitted! One happy Sprite owner! Just the padding to fit and we're off. The passenger seat will get its harness when I've sorted a problem with the sill mounting. We should have given it its first run out at the Loton Park test days last weekend but two foot of snow on the track put paid to that! Doing our best to be patient and ready to go for the first competition in a couple of weeks. I would have posted sooner if some clot hadn't snagged the overhead phone line and deprived the neighbourhood of phone and internet for over two weeks! Quite a lot of BBS catching up to do! Colin

Colin Mee

This thread was discussed between 10/02/2013 and 22/10/2023

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